Background and study aim: Endoscopic screening of all patients with liver cirrhosis add major burden to endoscopic units. Non-invasive detection of Oesophageal varices (OV) help to reduce the necessity of endoscopic screening.The aim of this work is to assess the diagnostic utility of blood ammonia level (BAL) as noninvasive predictor for presence of OV and evaluate its correlation with variceal size in cirrhotic patients. Patients and Methods: This prospective cross sectional study was conducted upon 100 cirrhotic patients who attended Hepatology, Gastroenterology and Infectious diseases department, Benha University Hospital. Fasting blood ammonia was measured and upper gastrointestinal endoscopy was done for all patients. Patients were divided according to presence of OV into two groups: Group I : included 30 patients with liver cirrhosis without OV. Group II: included 70 patients with liver cirrhosis with OV who were subdivided into four subgroups: Group IIa:included 11 patients with grade I O.V. Group IIb: included 21 patients with grade II O.V. Group IIc: included 15 patients with grade III O.V. Group IId: included 23 patients with grade IV O.V. Results: The study showed that there was a highly significant increase in the mean values of BAL in cirrhotic patients with varices in comparison to those without varices. Also the study showed highly significant increase in the mean values of BAL in patients with large OV (grade III,IV) in comparison to patients with small and medium sized varices (grade I,II). By multivariate analysis, the presence of O.V. was independently associated with increased blood ammonia levels. Conclusion: Blood ammonia level could be a non invasive predictor for the presence of OV and could be clinically useful, as it correlated with the size of OV.